Chen Zhaoyang

A study on the real-time radiation dosimetry measurement system based on optically stimulated luminescence

The optically stimulated luminescent (OSL) radiation dosimeter technically surveys a wide dynamic measurement range and a high sensitivity. Optical fiber dosimeters provide capability for remote monitoring of the radiation in the locations which are difficult-to-access and hazardous. In addition, optical fiber dosimeters are immune to electrical and radio-frequency interference. In this paper, a novel remote optical fiber radiation dosimeter is described. The optical fiber dosimeter takes advantage of the charge trapping materials CaS:Ce, Sm that exhibit OSL. The measuring range of the dosimeter is from 0.1 to 100 Gy. The equipment is relatively simple and small in size, and has low power consumption. This device is suitable for measuring the space radiation dose and also can be used in high radiation dose condition and other dangerous radiation occasions.

The study on optically stimulated luminescence dosimeter based on the SrS:Eu, Sm and CaS:Eu, Sm

With the increasing use of nuclear energy, there is a need for a wider range of effcient dosimeters for radiation detection and assessment. There has been a tremendous growth in the development of radiation detectors and devices in the past few decades. In recent years, the development of new materials for radiation dosimetry has progressed significantly. Alkaline earth sulfides (AES) have been known for a long time as excellent and versatile phosphor materials. In the present investigation, a number of phosphor samples such as mono-, binary and ternary sulfides of alkaline earths (IIa-VIb) have been prepared and their TL properties have been studied with respect to exposure (x-ray) response and fading. In this paper, some results on SrS:Eu, Sm and CaS:Eu, Sm phosphors are presented. A type of novel OSL dosimeter is described. The dosimeter takes advantage of the characteristics of charge trapping materials SrS:Eu, Sm and CaS:Eu, Sm that exhibit optically stimulated luminescence (OSL). The measuring range of the dosimeter is from 0.01 to 1000 Gy. The OSL dosimeters provide capability for remote monitoring radiation locations which are difficult to access and hazardous. This equipment is relatively simple, small in size and has low power consumption. The device is suitable for space radiation dose exploration. In addition, it also can be used in IC and other radiation occasions and has good prospects.

a novel process to synthesize nicomno4 nano-powder for ntc electro-ceramics

A pure spinel-type phase was attained by solid state reactions at room temperature, with no intermediate compounds. Its formation and the structural evolutions have been characterized by thermogravimetry-differential scanning calorimetry (TG/DSC) tests, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Related electrical analyses were also performed. The results showed that the powders and ceramics prepared by the solid state reactions at room temperature exhibit a good electrical property because of narrow grain size distribution, controlled morphology, and high purity. Most importantly, this new approach greatly simplifies the preparation processes.

Optical bistability in V medium by squeezed vacuum input

We discuss the optical bistable behavior of a system of N V-type three-level atoms pumped by a coherent input field and coupled to a squeezed vacuum field by treating the optical bistability of such a system as an input-output problem. It is shown that bistability can be realized due to the squeezed vacuum input.

Separation and Purification of Methane from coal-Bed Methane via the Hydrate Technology

The separation of methane from coal-bed methane (CBM) via hydrate process using tetrahydrofuran (THF) + sodium dodecyl sulfate (SDS) as additives was investigated in this work. The effect of additives, the concentration of the additives and hydrate memory effect on the hydrate-based separation process were examined at various concentrations of THF + SDS solutions. The results indicate that THF + SDS solutions decrease the formation pressure of methane remarkably and show that the methane concentration in CBM can be enhanced effectively with the system of THF (1.0 mol%) + SDS (500 ppm) in the moderate condition. The concentration of CH4 can be increased by about 20% for the two feed gases (20% and 50% CH4/N2). It indicates the CBM with low methane can be improved to the one which can be used directly by several steps of the hydrate-based separation technology.

Dose-rate dependence of optically stimulated luminescence signal

Optically stimulated luminescence (OSL) is the luminescence emitted from a semiconductor during its exposure to light. The OSL intensity is a function of the total dose absorbed by the sample. The dose-rate dependence of the OSL signal of the semiconductor CaS doped Ce and Sm was studied by numerical simulation and experiments. Based on a one-trap/one-center model, the whole OSL process was represented by a series of differential equations. The dose-rate properties of the materials were acquired theoretically by solving the equations. Good coherence was achieved between numerical simulation and experiments, both of which showed that the OSL signal was independent of dose rate. This result validates that when using OSL as a dosimetry technique, the dose-rate effect can be neglected.

NTC and electrical properties of nickel and gold doped n-type silicon material

Silicon materials compensated by deep level impurities such as nickel and gold have negative temperature coefficient (NTC) characteristics. In this work, n-type silicon wafers are smeared by nickel chloride ethanol solution and gold chloric acid ethanol solution, and subsequently put in the opening environment to heat. The electrical resistance and B-value of the thermistors made by this silicon material are measured and analyzed. When the silicon surface concentration of gold atoms is 2 × 10−6 mol/cm2, the uniformity of the single-crystal silicon material is optimal. When the diffusion temperature is between 900 and 1000 °C, a material with high B-value and low electrical resistivity is obtained. The B–T and R–T change laws calculated by the theory of semiconductor deep level energy are basically consistent with the experimental results.

Influence of Squeezed Vacuum on Bistable Behavior

The influence of squeezed vacuum input on the optical bistable behavior of a system of N three-level atoms which are simultaneously coupled to a coherent pump field and a squeezed vacuum input is investigated. It is shown that the squeezed vacuum will significantly increase the range of the optical bistability and this effect is phase-sensitive. The results exhibit that the optical bistability can be controlled by the squeezed vacuum input.

Dynamics of Interaction of H2+ with Intense Ultrashort Laser Pulse

The dynamic process of H2+ in intense ultrashort laser pulses with intensities of 1014 ~ 1015 W/cm2, wavelength of 532 nm and duration of 22 fs is theoretically investigated by using collinear model and numerically solving the time-dependent Schr?dinger equation. The results show that: (1) the dissociation and dissociative ionization compete each other in the case of intensities between 2.5 ? 1014 and 4.0 ? 1014 W/cm2; (2) both the dissociation and the dissociative ionization are much smaller and appear at about 5 cycles (?9 fs) later than the ionization. In addition, we estimate the spectrum of high harmonic generation and find that the well-known cutoff rule is invalid for the ultrashort laser pulse (e.g. the duration???25 fs), because the shorter pulse can produce higher order harmonics than the longer one.

Dynamics of H2+ in two-color ultrashort laser pulse

Numerical simulations of ionization and dissociation processes of hydrogen molecular ion H2+ interacting with two-color intense ( 1014W/cm2-1015W/cm2) ultrashort (the duration ≈ 22fs) laser pulse are made. The result shows that the ionization and dissociation processes are strongly dependent upon the relative phase between the two color fields. It means that, in the case of ultrashort pulse, the phase coherence control of ionization and dissociation processes can be realized.